The present invention relates to liquid fuel burners of the type wherein the rate of fuel vaporization is chiefly governed by the heat of its own flame with which recirculated air of an enclosed indoor space is warmed, and more particularly to a liquid fuel burner of such type having a safety device operable in response to the occurrence of an oxygen shortage condition.
Oxygen sensors are currently employed as a means for detecting oxygen shortage conditions which are likely to occur in liquid fuel burners of the primary combustion type wherein the fuel is vaporized by an external heat source or in gas burners. The oxygen sensor, either of a partial pressure type or of a concentration differential type, is currently located in an environment which is downstream of the flame and in which the oxygen's partial pressure or concentration is high when the burner is properly operating so that when an oxygen shortage condition occurs the flame extends to such a degree that it encloses the oxygen sensor and as a result the sensor's oxygen environment switches to a low partial pressure or concentration state.
While the current practice is effective for the burners of the type just mentioned, the current practice does not apply to liquid fuel burners of the type such as kerosene heaters and pot burners wherein the rate of fuel vaporization is chiefly governed by the heat produced by its own vaporized fuel since the flame diminishes under oxygen shortage conditions. Therefore, the downstream point of the flame is predominantly of a carbon monoxide environment and the oxygen sensor, if located thereat, would not provide a valid indication. With burners in which secondary air is introduced for combustion of unburned fuel, there is no distinct variation in the amount of oxygen at the downstream point.